Implantable electrode with stiffening stylet



@et 24, 1967 W. M. CHARDACK 3,348,548

IMPLANTABLE ELECTRODE WITH STIFFENING STYLET 2 Sheets-Sheet 22 FiledApril 26, 1965 HUUHH HUI HIHIHIHHIHHIHHI HH INVENTOR Zz/Zcmz 772 CUPCZQel? Qbw/V/ United States Patent O 3,348,548 IMPLAN'IABLE ELECTRUDE WITHSTIFFENING STYLET William M. Chardack, 144 Ivyhurst Road, Buffalo, NY.14226 Filed Apr. 26, 1965, Ser. No. 450,910 9 Claims. (Cl. 12S-418) Thisinvention relates to a new and useful electrode especially adapted forimplantation within the human body.

In certain cases of heart disease the impulses which normally elicitcontraction of the cardiac ventricle are blocked. This leads to anabnormally low heart rate severely restricting the patients activities.Episodes of complete arrest occur in this condition leading to loss ofconsciousness which may terminate fatally. In some patients, thecondition cannot be controlled short of electrical stimulation of theheart. A number of devices, known as Pacemakers have been developed forthis purpose. They provide a suitable stimulating current pulse. Some ofthese devices are external, some are suitable for complete implantationwithin the body, and some are partly external and operate by inductionthrough the intact skin through a subcutaneously buried coil. In mostmethods, the impulse ultimately travels to the heart muscle by anelectrode at its leads, either from an external Pacemaker through theskin and deeper tissue to the heart muscle or from a subcutaneouslyimplanted Pacemaker or an induction coil to the heart.

The provision of an electrode suitable for implanting in the heartmuscle presents a severe problem, because of the varied motions whichmust be accompanied. The primary requirement of such an electrode, andconnecting lead, are that they be flex-resistant to a high degree. Thatis to say, they must be capable of 'withstanding constantly, rapidlyrepeatedl flexing over a long period of time. For example, if the heartis stimulated once each second, there will be 60 flexing actions eachminute, or more than 30 million flexing actions each year. The conductorand its insulation must be capable of withstanding repeated lateral andaxial flexing on this order, without failureproducing fatigue. Inaddition, they must be able to withstand momentary elongation, such asproduced by movement of the chest cavity during respiration, and by bodymotion as when bending, stretching and the like, as well as by motion ofthe heart. Also, when implanted in a youth whose body size willincrease, the electrode and lead must be capable of accommodating suchgrowth.

A Pacemaker electrode can be inserted through a vein and come to lie oncontact with the inner lining of the heart. This is a desirabletechnique, because it avoids opening the chest cavity and can beperformed under local anesthesia. As a result, it is particularlyvaluable for patients in whom a thoracotomy is contraindicated orcarries a prohibitive risk.

However, a further problem arises where this technique is used, becausean electrode having the requisite flexibility enabling it to withstandconstantly, rapidly repeated flexing over a long period of time is tooflexible to lbe advanced through the vein and directed into theappropriate position in the heart.

Accordingly, a primary object of my invention is to provide an electrode'which is capable of withstanding the above-designated forces over aperiod of years, and which also is adapted for insertion into the heartthrough a vein.

In one aspect thereof, an electrode constructed in accordance with myinvention is characterized by the provision of electrical conductors allof closely coiled construction enclosed within a sleeve of electricallyinsulating material, the conductors extending lengthwise of the sleeveand beingrinsulated from each other, and a stylet also extendinglengthwise of the sleeve, the stylet providing rigidly enablinginsertion of the electrode through a vein and being removable from theelectrode ot restore optimal flex life thereto.

The foregoing and other objects, advantages and characterizing featuresof an electrode of my invention will become clearly apparent from theensuing detailed description of two illustrative embodiments thereof,taken together with the accompanying drawings depicting the same whereinlike reference numerals denote like parts throughout the various viewsand wherein:

FIG. 1 is a view of one form of electrode of my invention, showing astylet in place therein;

FIG. 2 is a longitudinal seectional view thereof, on an enlarged scale,through the terminal end of the electrode;

FIG. 3 is a View partly in side elevation and partly in longitudinalsection of the contact end portion of the electrode;

FIG. 4 is a longitudinal sectional view through the contact end of theelectrode, on a further enlarged scale;

FIGS. 5 and 6 are transverse sectional views on a still further enlargedscale, taken about on lines 5-5 and 6 6, respectively, of FIG. 3;

FIG. 7 is a fragmentary side elevational view of the electrode, on thescale of FIG. 2 and with the stylet partly removed;

FIG. 8 is a view, partly in plan and partly in longitudinal section,showing the terminal end of another form of electrode of my invention;and

FIG. 9 is avtransverse sectional view thereof, on an enlarged scale,taken about on line 9-9 of FIG. 8.

Referring now to the embodiment of FIGS. 1 7, there is shown anelectrode of my invention comprising an elongated lead portion l, acontact end portion 2 and a terminal end portion 3. The electrodecomprises a pair of closely wound, coiled conductors 4, 5 each in theform of a spring spirally wound about and along the axis of theconductor. The spring coils 4, 5 travel in separate lumens ofa jacket orsleeve 6 of electrically insulating material.

Each conductor 4, 5 is formed of electrically conductive materialoffering low electrical resistance and also resistant to corrosion bybody fluids. Stainless steel is an example of a suitable material.Sleeve 6 is formed of an electrically insulating material, andpreferably a silicone rubber such as medical grade Silastic availablefrom Dow Corning Corporation. This material is additionally suitablebecause it is inert and well tolerated by body tissue.

Pins 7 of stainless steel or other suitable material are` inserted intothe open lumen of the conductor coils 4 and 5, at the contact endsthereof, and these coil ends then are welded to electrode contacts 8 and9. These contacts must be electrically conductive and resistant tocorrosion by body fluids, and I have found platinum to be especiallysuitable. Contact 8 comprises a ring encircling both coils 4 and 5, andthe contact end of sleeve 6. Contact 9 comprises a cup at the end of theelectrode, enclosing the contact end of coil 4 which extends beyond coil5 in a reduced diameter extension lil* of sleeve 6, as clearly shown inFIG. 4. A jacket ll of the same material as sleeve 6 is molded about thecontact ends of coils 4 and 5, and about the sleeve extension 10, withinthe contact ring 8 and contact cup 9, as clearly shown in FIG. 4. Inthis way, the contact end 2 of the electrode is completely insulated,except for the contacts 8` and 9. It will be appreciated that after themolding operation jacket 11 and sleeve 6 become integral.

At their opposite ends, coils 4 and 5 are received in tubular terminalsl2, 13 which are crimped in place on the conductor coils. A bifurcatedboot 14- of the same material as jacket 6 is molded about the terminals12, 13 and the terminal ends of coils 4 and 5, and jacket 6, with theterminals 12 and 13 projecting therebeyond. These terminals are adaptedfor insertion in receptacles provided on the pulse generator, which cancomprise any suitable Pacemaker such as that shown for example in UnitedStates Patent 3,057,356 which may have provision for percutaneousadjustment of rate and amplitude in accordance with my pendingapplication Ser. No. 231,349, now Patent No. 3,198,195.

The electrode construction thus far described is capable of withstandingconstant, rapidly repeated flexing over a period of time which can bemeasured in years. The conductor coils are wound relatively tightly,although there can be a slight space between adjacent turns. Thisclosely coiled construction provides a maximum number of conductor turnsper unit length, thereby providing optimum strain distribution. Thespirally coiled spring construction of the conductors also permits asubstantial degree of elongation, within the elastic limits of thematerial, as well as distribution along the conductor of llexingstresses which otherwise might be concentrated at av particular point.Both the conductors 4 and 5, and the insulating bodies 6, 11 and 14 areelastic, and this, together with the coiled construction of theconductors, assures maximum distribution of flexing strains.

In addition to insulating the conductor coils 4 and 5, the bodies 6, 11and 14 prevent ingrowth of tissue between convolutions of the conductorcoils.

However, this very flexing characteristic, so essential to long life anddependability of the electrode, works against its adaptability forinsertion through a vein, and renders it generally unsuitable for suchmethod of implantation. Therefore, it is a particular feature of myinvention that the electrode incorporates means facilitating itsinsertion through a body passage such as a vein, in the manner of acatheter, without impeding its flexing characteristics after theelectrode is in place. This is accomplished by inserting in the openpassageway or lumen through either coil 4, 5, or both of them, a stylet(FIGS. l and 7). In practice, the stylet or stylets, as the case may be,is furnished with the electrode as a removable part thereof. Each stylet15 is formed of stainless steel or other material suitable for thepurpose, and comprises for example a cylindrical wire closely tting theinner wall of the conductor coil with sufficient clearance therebetweenfor insertion and removal of the stylet. For example, where the coil 4or 5 is wound on a mandrel of .016i inch dia., a stylet 15 having anouter diameter of .014 inch or .015 inch can be used.

The stylet 15 stiffens the electrode. Its distal end, at the contact end2 of the electrode, is bent slightly, while its proximal end, adjacentthe terminal end 3 of the electrode, is formed to provide means, such asthe loop 16, for rotating the stylet about its axis to thereby directthe contact end 2 of the electrode as it is inserted through the vein.The stylet imparts rigidity to the proximal portion of the electrode,and introduces the` appropriate curvature to the distal, contact endportion facilitating the insertion of the electrode into and through avein, for example one of the jugular veins, to advance the contact end 2of the electrode into the right ventricle of the heart.

Once the electrode has been properly positioned, the stylet 15 is'retracted and withdrawn from the conductor 4, completely separating itfrom the electrode, the terminals 12 and 13 of which then can beinserted into the Pacemaker sockets. This restores the electrode to itsoptimal condition in regard to tolerance of flexing stresses.

In the embodiment of FIGS. 1-7 the stylet is inserted through the openend of terminal 12 and through coil 4 (and/or through terminal 13 andcoil 5, as the case may be) it being understood that the crimping of theterminals on the -coil ends does not interfere with passage of thestylet through the terminals and coils. This means that 4 the stylet orstylets must be removed from the electrode before the electrode isconnected to the Pacemaker.

Sometimes, however, it is desired to have the stylet in placetemporarily, with the electrode connected to the Pacemaker, and to beable to remove the stylet without having to dismantle thePacemaker-electrode junction with its seal. This can be accomplishedwith the f-orm of electrode shown in FIGS. 8 and 9. In this embodiment,the lead portion includes an insulating jacket 60 of the same materialas jacket 6 but formed with three lumens therethrough. Two of the lumensreceive the conductor coils 4 and 5, in the same manner as before. Thethird lumen receives a lining sleeve 17 `of a flexible material whichpermits easy sliding of the stylet. Teflon with its selflubricatingproperties and its inertness in body tissue is particularly suitable.Sleeve 17 extends lengthwise within jacket 60 to the contact end andprojects through the crotch of the terminal jacket 14. The stylet 15 isinserted through the sleeve 17. The contact end, not shown, of theelectrode of FIGS. 8 and 9 is identical with the contact end 2 in theembodiment of FIGS. 1-7. The terminals 12 and 13 are of stainless steelor other suitable material, as in the case of the FIGS. 1-7 embodiment,but their outer ends can be closed if desired because the stylet -doesnot pass through the end terminals. Instead, it passes through thesleeve 17 from which it can be withdrawn after the electrode has beenconnected and sealed to the Pacemaker. For instance, this can beaccomplished at any time after implantation of the assembly and withonly a minute incision.

It will be appreciated that the stylet 15 serves the same function inthe embodiment of FIGS. 8 and 9 as it did in the embodiment of FIGS.1-7. The self-lubricating sleeve 17 facilitates insertion of the styletthrough the sleeve, as distinguished from the resistance to suchinsertion which would be felt if the stylet were in contact with thesilicone rubber of the jacket 60.

While substantial clearance has been shown between stylet 15 and sleeve17, for ease of illustration in FIG. 9, it will be appreciated thatessentially only sliding clearance is provided. With the styletwithdrawn, the electrode has the desired flexing characteristics andlong flex life as previously described in connection with the embodimentof FIGS. 1-7.

It will be noted that the jacket 6 is flat sided, and rectangular,whereas the jacket 60 is circular. The rectangular form of the jacket 6imparts directional bending characteristics to the electrode.

Accordingly, it is seen that my invention fully accomplishes itsintended objects. While I have disclosed and described in detail onlytwo embodiments of my invention, that has been done by way ofillustration, and not by way of limitation. I lrealize that an electrodeof my invention can assume additional forms, and I intend to includewithin the scope of the appended claims all modiactions and variationsnaturally occurring to those skilled in the art.

Having fully disclosed and completely described my invention, and itsmode of operation, what I claim as new is:

1. In an electrode adapted for permanent implantation in an animal body,a sleeve of electrically insulating material having separate lumenstherein, a coiled electrical conductor in one of said lumen, and aremovable stylet in another of said lumen, said stylet impartingrigidity to said electrode for insertion thereof through a vein to theheart.

2. In an electrode adapted for permanent implantation in an animal body,a sleeve of electrically insulating material, a pair of coiledelectrical conductors extending lengthwise within said sleeve, a styletalso extending lengthwise within said sleeve, said stylet impartingrigidity to said electrode for insertion thereof through a vein to theheart and being removable endwise from said electrode to restore theflexibility thereof.

3. In an electrode adapted for permanent implantation in an animal body,a body of electrically insulating material, electrically conductivemeans consisting entirely of spirally wound electrical conductorextending lengthwise within said body, and a removable stylet alsoextending lengthwise within said body, said stylet imparting rigidity tosaid electrode for insertion thereof through a vein into the heart.

4. In an electrode adapted for implantation in an animal body, a sleeveof electrically insulating material having separate lumens therein, aclosely coiled electrical condu-ctor in one of said lumens, a liner ofself-lubricating material in another of said lumens, and a stylet insaid other lumen, said stylet providing rigidity to said electrode forinsertion through a vein to the heart and being removable from saidother lumen.A

5. In an electrode adapted for implantation in an animal body, a sleeveof electrically insulating material, a pair of closely coiled electricalconductors extending lengthwise of said sleeve, said coils beinginsulated by said sleeve, at least one of said conductors being openalong its axis from one end thereof, and a stylet inserted in said oneconductor, said stylet providing rigidity to said electrode forintralumenal insertion thereof and being removable from said conductorthrough said one end thereof for optimal flex life.

6. An electrode adapted for long-term implantation in an animal bodycomprising an elastic sleeve of electrically insulating materialresistant to adhesion of body tissue, a pair of closely coiledelectrical conductors extending lengthwise within said sleeve in spacedapart insulated relation, a pair of contacts `connected to said coilsadjacent one end of said sleeve, a pair of terminals connected to saidcoils adjacent the opposite end of said sleeve, a separate passagewaythrough said sleeve from the terminal end thereof substantially to thecontact end thereof, and a stylet inserted in said passageway, saidstylet providing ridigity to said electrode for insertion thereofthrough a vein to the heart and being removable from said passageway torestore flexibility to said electrode.

7. An electrode adapted for long-term implantation in an animal bodycomprising an elastic sleeve of electrically insulating materialresistant to adhesion of body tissue, a pair of closely `coiledelectrical conductors extending lengthwise within said sleeve, a pair ofcontacts connected to said coils adjacent one end of said sleeve, a pairof terminals connected to said coils adjacent the opposite end of saidsleeve, at least one of said conductors and its terminal being open toprovide a passageway through said one terminal and substantially throughsaid one conductor, and a stylet inserted through said one terminal intosaid one conductor, said stylet providing rigidity to said electrode forinsertion thereof through a vein to the heart and being removable fromsaid one conductor and terminal.

8. An electr-ode as set forth in claim 3, wherein said removable styletis inserted in said conductive means.

9. An electrode as set forth in claim 3, wherein said stylet extendslengthwise of said body externally of said conductive means.

References Cited UNITED STATES PATENTS 789,161 5/ 1905 Linn 128-409 X2,164,926 7/1939 Kleine 128-349 2,774,382 12/ 1956 Bentley 174-47 X2,976,865 3/ 1961 Shipley 12S-2.05 3,035,583 5/ 1962 Hirsch et al 12S-418 X FOREIGN PATENTS 910,371 6/ 1946 France.

RICHARD A. GAUDET, Primary Examiner.

W. E. KAMM, Assistant Examiner.

3. IN AN ELECTRODE ADAPTED FOR PERMANENT IMPLANTATION IN AN ANIMAL BODY,A BODY OF ELECTRICALLY INSULATING MATERIAL, ELECTRICALLY CONDUCTIVEMEANS CONSISTING ENTIRELY OF SPIRALLY WOUND ELECTRICAL CONDUCTOREXTENDING LENGTHWISE WITHIN SAID BODY, AND A REMOVABLE STYLET ALSOEXTENDING LENGTHWISE WITHIN SAID BODY, SAID STYLET IMPARTING RIGIDITY TOSAID ELECTRODE FOR INSERTION THEREOF THROUGH A VEIN INTO THE HEART.